If you have a look at some 'bento' suppliers you will find all sorts of tings to use instead of a fork, eg little plastic, er they are animals with a fork bit that you put cherry tomatoes or fruit on to. There are some that are more like blunt cocktail sticks and tiny sauce jars. And silicon 'cups'.
Things like rice balls, meat balls or things like chicken tikka can be 'stuck'.
In a food flask you could do soup and things like baked beans, beans and sausage - maybe a bit hot for that at the moment. Unless he will eat chilled soup.
|How old is he? The bento egg moulds press the yolk of boiled eggs in to the white so they don't fall apart, great if your ds is 5, not if he is 15.
Tinned meat and fish, things like tuna and mackerel.
Canape type things, maybe made into a mini kebab so maybe a bit of cheese, a cherry tomato and a spring onion on a bento stick.
Rolled omelettes cut into cubes.
I also agree with cutting a sandwich into pieces.